== Running PO Simulations ==
[[File:PO27.png|thumb|400px|EM.Illumina's Simulation Run dialog.]]
[[File:PO28.png|thumb|350px|EM.Illumina's Simulation Engine Settings dialog.]]
Once you have set up your structure in EM.Illumina, have defined sources and observables and have examined the quality of the structure's mesh, you are ready to run a Physical Optics simulation. EM.Illumina offers five simulation modes (click on each type to learn more about it):
* '''[[Building_Reusable_Models#Running_an_HDMR_Sweep | HDMR Sweep]]'''
[[File:PO27.png|thumb|400px|EM.Illumina's Simulation Run dialog.]]
You can set the simulation mode from EM.Illumina's "Simulation Run Dialog". A single-frequency analysis is a single-run simulation. All the other simulation modes in the above list are considered multi-run simulations. If you run a simulation without having defined any observables, no data will be generated at the end of the simulation. In multi-run simulation modes, certain [[parameters]] are varied and a collection of simulation data files are generated. At the end of a sweep simulation, you can graph the simulation results in EM.Grid or you can animate the 3D simulation data from the navigation tree.
=== Setting The Numerical Parameters ===
[[File:PO28.png|thumb|350px|EM.Illumina's Simulation Engine Settings dialog.]]
Before you run a PO simulation, you can change some of the PO simulation engine settings. While in the [[PO Module]]'s '''Simulation Run Dialog''', click the '''Settings''' button next to the '''Select Engine''' dropdown list. In the Physical Optics Engine Settings Dialog, there are two options for '''Solver Type''': '''Iterative''' and '''GOPO'''. The default option is Iterative. The GOPO solver is a zero-order PO simulator that uses Geometrical Optics (GO) to determine the lit and shadow cells in the structure's mesh. For the termination of the IPO solver, there are two options: '''Convergence Error''' and '''Maximum Number of Iterations'''. The default Termination Criterion is based on convergence error, which has a default value of 0.1 and can be changed to any desired accuracy. The convergence error is defined as the L2 norm of the normalized residual error in the combined '''J/M''' current solution of the entire discretized structure from one iteration to the next. Note that for this purpose, the magnetic currents are scaled by η<sub>0</sub> in the residual error vector.